.wikiheaders-options: Removed wikipreamble setting.

Reference https://github.com/libsdl-org/sdlwiki/issues/713.

.wikiheaders-options

@@ -14,7 +14,7 @@ projecturl = https://libsdl.org/
 wikiurl = https://wiki.libsdl.org/SDL2
 bugreporturl = https://github.com/libsdl-org/sdlwiki/issues/new
 warn_about_missing = 0
-wikipreamble = (This is the legacy documentation for SDL2, the previous stable version; [SDL3](https://wiki.libsdl.org/SDL3/) is the current stable version.)
+#wikipreamble = (This is the legacy documentation for SDL2, the previous stable version; [SDL3](https://wiki.libsdl.org/SDL3/) is the current stable version.)
 wikiheaderfiletext = Defined in [%fname%](https://github.com/libsdl-org/SDL/blob/SDL2/include/%fname%)
 manpageheaderfiletext = Defined in %fname%